Work will be continued on the following problems: 1. The resolution and reconstitution of a subcellular plasma membrane vesicle system from pigeon red cells capable of amino acid active transport. 2. The transport-induced separation by density gradient centrifugation of transport-active membrane vesicles from inactive ones. This is aimed at the identification of porter components and of membrane domains. 3. Effects of exogenous lipids on transport activity which may be relevant to arteriosclerosis. 4. The compartmentation of Na ion in pigeon red blood cells.